Jumpin’ Jehoshapat! New grasshopper-like material can jump 200 times its own thickness – ScienceDaily


Engineers at the University of Colorado Boulder have designed a new rubber-like film that can leap high into the air like a locust—all on its own and without the need for outside intervention. Just heat it up and watch it jump!

The researchers describe their achievement in the January 18 issue of the journal Science advances. They say similar materials could one day help make “soft robots” (those that don’t need gears or other rigid components to move them) jump or lift.

Study co-author Timothy White said the compound responds somewhat like how grasshoppers jump by storing and releasing energy in their legs.

“In nature, a lot of adaptations like a grasshopper’s leg use stored energy, like elastic instability,” said White, Gallogly Professor of Chemical and Biological Engineering at CU Boulder. “We’re trying to make synthetic materials that mimic those natural properties.”

The new research takes advantage of the unusual behavior of a class of materials called liquid crystal elastomers. These materials are rigid, stretchy polymer versions of the liquid crystals found in laptop computers or television screens.

In the study, the team made tiny flakes of liquid crystal elastomer about the size of a contact lens, then placed them on a hot plate. As these films heated up, they began to warp, forming a cone that rose until suddenly and explosively, it flipped inside out—shooting material nearly 200 times its thickness in just 6 milliseconds.

“This provides opportunities to use polymer materials in new ways for applications such as soft robotics where we often need access to high-speed, high-force actuation mechanisms,” said lead study author Tyler Hebner, who has a Ph.D. in chemical and biological engineering. at CU Boulder in 2022.

Serendipitous discovery

Hebner, now a postdoctoral researcher at the University of Oregon, and her colleagues discovered this jumping behavior almost by accident.

She was experimenting with different types of liquid crystal plastics to see how they changed shape under changing temperatures. Joselle McCracken, a senior research associate in White’s lab, joined her to observe.

“We were just watching the rubbery liquid crystal material lay on the hot plate and wondering why it wasn’t making the shape we expected,” Hebner said. “It suddenly jumped out of the test stage and straight onto the table top.” We both looked at each other confused but also excited.

Through careful experimentation and help from collaborators at Caltech, the team figured out what makes their materials make the high jump.

White explained that each of these films consists of three layers of elastomer. He said that these layers shrink when they get hot, but the top two layers shrink faster than the bottom layer. This discrepancy, together with the orientation of the liquid crystal molecules within the layers, causes the film to shrink and form a conical shape. It’s a bit like how painted vinyl edges can roll in the sunshine.

As the cone forms, pressure builds up in the film until it bursts all at once! The cone turns over, hitting the surface and knocking the material. The same movie can also be jumped multiple times without running out.

“When this inversion occurs, the material explodes and, like a baby popper, jumps off the surface,” White said.

leaps forward

Unlike those poppers, the team’s liquid crystal elastomers are very versatile. Researchers can modify their films so that they jump when they get cold, for example, not hot. They can also give the films legs to make them jump in a certain direction.

Most robots probably won’t be able to use this kind of popping effect to move their parts. But White said the project shows similar types of materials might be able to store a huge amount of elastic energy, and then release it all at once. Hebner said the project brought some fun to the lab.

“It’s a powerful example of how we can turn basic concepts we study into designs that perform in complex and surprising ways,” she said.

Grasshoppers, face your new rival.

Video: https://youtu.be/0iggefqpACQ



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